Influence of 6-diazo-5-oxo-L-norleucine (DON), a glutamine analogue, on cartilaginous differentiation in mouse limb buds in vitro.

The antibiotic, 6-diazo-5-oxo-L-norleucine (DON), an analogue of L-glutamine, causes limb malformations in several species, including mice. This report shows that DON also interferes with differentiation of cartilaginous rudiments of mouse limb buds grown as organ cultures for 3 to 8 days in medium containing the teratogen. DON (5 mug/ml) inhibits growth of the explants and interferes with production of normal matrix by chondrocytes. The cartilage of DON-treated cultures exhibits a striking lack of matrix, compared with that of control explants which contains abundant metachromatic matrix. Differentiation of osteoblasts, and secretion of osteoid around the scapula and humerus are enhanced by DON. The direct effects of DON on growth and chondrogenesis, which can be prevented by addition of L-glutamine (1 mg/ml) to the medium, can be attributed to the known interference of DON in L-glutamine-dependent steps in metabolism. The possible relationships between these effects of DON in vitro and the malformations produced in vivo, are discussed.